Elevator and method for tilting solid image build platform for reducing air entrainment and for build release

ABSTRACT

A solid imaging apparatus is provided that includes a replaceable cartridge containing a source of build material and an extendable and retractable flexible transport film for transporting the build material layer-by-layer from the cartridge to the surface of a build in an image plane. An operator using the device needs merely to remove a spent cartridge and replace it with a fresh cartridge to continue solid imaging virtually uninterrupted. The apparatus also includes the capability of withdrawing and inserting an imager without the operator having to perform a separate alignment step. A brush attached to the transport film and forming part of the cartridge provides for intra-layer removal of excess uncured build material. If desired, the apparatus can produce a fully reacted build. A high intensity UV source cures the build between layers. An injection molded build pad is designed to hold a build in an inverted position for improving the build. The invention also provides for tilting the build elevator to reduce air entrainment and for releasing the build from the image plane.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.11/856,225, filed Sep. 17, 2007 now U.S. Pat. No. 8,003,039, which ishereby incorporated herein in its entirety by reference.

This application claims priority from Provisional Application Ser. No.60/885,257 filed Jan. 17, 2007 for “Solid Imaging Apparatus and MethodIncluding: Cartridge for Solid Imaging Apparatus; Method for ConveyingBuild Material Layer-By-Layer; Elevator for Tilting Solid Image BuildPlatform for Reducing Air Entrainment and for Consistent RepeatableAlignment in a Solid Imaging Apparatus;” Provisional Application Ser.No. 60/949,614 filed Jul. 13, 2007 for “Solid Imaging Apparatus, andMethod Including: Cartridge for Solid Imaging Apparatus; Method forConveying Build Material Layer-by-Layer; Elevator for Tilting SolidImage Build Platform for Reducing Air Entrainment and for Build Release;Build Platform, Solid Image, and Method for Solid Imaging; Imager andMethod for Consistent Repeatable Alignment in a Solid Imaging Apparatus;Eccentric Reciprocating Brush and Method for Reducing Overbuild; andProvisional Application Ser. No. 60/956,051 filed Aug. 15, 2007 for“Solid Imaging Apparatus and Method Including: Cartridge for SolidImaging Apparatus; Method for Conveying Build Material Layer-By-Layer;Elevator for Tilting Solid Image Build Platform for Reducing AirEntrainment and for Build Release; Build Platform, Solid Image, andMethod for Solid Imaging; Imager and Method for Consistent RepeatableAlignment in a Solid Imaging Apparatus; and Intra-Layer CleaningAssembly and Method for Removing Excess Uncured Build Material;” thecontents of which are incorporated herein by reference in theirentirety.

FIELD OF INVENTION

This invention relates to solid imaging apparatus and methods.

BACKGROUND

Solid imaging devices have been used for rapid prototyping for modelsfor product development, and, more recently, for manufacturingoperations. Solid imaging devices produce three-dimensional objects fromfusible powders or photocurable liquids, typically by exposure toradiation in response to computer control. Data representing thincross-sectional layers of a three-dimensional object provide thecomputer with control parameters for programs for automated building ofthe object, typically layer-by-layer. A laser or other source ofradiation suitable for solid imaging sequentially irradiates individualthin layers of the build material in response to which the materialtransforms into a solid, layer-upon-layer, to create a solid imagingproduct.

Solid imaging is sometimes referred to as “rapid prototyping andmanufacturing” and includes such diverse techniques asstereolithography, laser sintering, ink jet printing, and others.Powders, liquids, and other materials for solid imaging sometimes arereferred to as “build materials” and the three-dimensional objects thatsolid imaging produces sometimes are called “builds,” “parts,” and“solid imaging products,” which can include a variety of shapes. Thebuilds are usually prepared on surfaces referred to as “build pads” or“build platforms” that can be raised or lowered to place the surface ofa build into contact with imaging radiation. The area where the buildmaterial is exposed sometimes is referred to as the “build plane” or“image plane.”

Despite the variety of devices and methods developed for solid imaging,a number of drawbacks have yet to be resolved. The apparatus and methodsfor practicing solid imaging tend to be somewhat characterized byexcessive moving parts and complex systems that can require a good dealof effort to service, maintain, and operate. Laser imaging and UVimaging systems tend to be costly and to place these systems out ofreach for many applications. Complex, tedious alignment steps foraligning the radiation source and the image plane reduce efficiency andincrease cost. The large vats of liquid resin used in stereolithographyare expensive and can become contaminated with pieces of cured resin.Solid imaging devices typically produce “green” three-dimensionalproducts, in which uncured build material wets the surface and causesthe product to be tacky and to require cleaning prior to fully curingthe product throughout the build.

It would be desirable to provide solid imaging systems and methods thatreduce service and maintenance problems and that are simpler to operate,less costly, and more efficient.

SUMMARY OF THE INVENTION

The invention relates to solid imaging apparatus and methods that havebeen completely redesigned from the ground up with a number ofsubassemblies to provide improved systems, including a replaceablecartridge assembly that contains the build material, a transport surfacefor transporting build material from the cartridge to the build planelayer-by-layer, and a cleaning assembly attached to the transportsurface for removing excess uncured build material from the buildbetween application of layers. The cartridge of the invention does notspill during storage or transport, is sealed against light, and is notactivated for dispensing build material until inserted into theapparatus and switched on by an operator. An operator of the systemmerely has to remove and replace the spent cartridge with a freshcartridge containing new build material, disposing of or recycling thespent cartridge.

In a specific embodiment of the cartridge, a flexible film typicallyserves as the transport surface. The cartridge provides a housingcontaining the build material, a pump for supplying the build materialto the film, and an internal assembly for storing the film and cleaningassembly that cooperates with external motors for coating the film withbuild material, extending the film, and retracting the film. The filmattaches to the cleaning assembly by which assembly the film isextended. The cleaning assembly includes a brush for contacting thebuild to remove excess uncured build material as the film is retractedand the excess uncured build material is returned to the cartridgehousing for filtration and reuse.

The invention provides an imager assembly for a solid imaging device inwhich the imager assembly includes an alignment fixture that is fixedlyattached to the imager for precision mounting of the imager to the solidimaging apparatus. An operator of the apparatus can simply remove andreplace the imager without additional complex alignment steps. Theimager illuminates the build from underneath.

The invention includes a high-intensity UV lamp, in the range ofapproximately 600 Watts, and associated cooling channels for air flow,the UV lamp illuminating the build from the bottom for curing operationsfor each layer of the part after imaging and cleaning. Builds producedby the apparatus have substantially reduced or no tackiness and can beproduced in a fully cured state within the apparatus.

In one embodiment, the build pad includes on one side raiseddiscontinuous surfaces forming a grid upon which a lattice can be builtfor the support surfaces for the build, enhancing the bond to the buildpart and better enabling the part to be built in an upside downposition. Holding the build in an upside down position facilitatesbuilding with less excess uncured build material on the build. The buildpad includes on its opposite side raised discontinuous surfaces forminga grid for the purpose of supporting the build pad under vacuum againsta ground, flat metal build platform. A vacuum seal is included about theperiphery of this build pad side.

In another embodiment, the build pad is transmissive to curing radiationand does not include the vacuum supporting grid, and the build platformis a bracket providing for unobstructed application of curing radiationto the build and supports through the build pad. In this embodiment,multiple UV assemblies of relatively lower wattage, of around 100 Watts,are provided for intra-layer curing, normally without the higherintensity UV source.

Elevator arm assemblies reduce the possibility of air entrainment in thebuild and facilitate release of the build from the transport surface.Independently operated elevator arms slightly tilt a retaining frame andsupporting platform for the build pad as the build pad approaches thebuild material on the transport surface in the image plane. Tilting onapproach provides a path for air to escape. Tilting the build platformafter imaging has take place while lifting the build off the transportsurface facilitates release of the build from the transport surface.

The cartridge assembly with its transport surface, coating and cleaningassembly, and build material, the imager assembly and additionalpost-curing assemblies, the build pad and grid, the elevator assemblieswith the tilt feature, and additional assemblies and features cooperateto promote production of drier, cleaner, more precise and fully curedbuilds by solid imaging. The transport surface enables the invention tobe used in a flexible transport imaging apparatus. The cartridge, imagerand post curing assemblies, build pad, elevator assemblies, andadditional features can be combined in a small format, including a desktop modeler format, if desired.

Thus, the invention provides, among other things, a desk top modeler forflexible transport solid imaging providing removable and replaceableconsumable components of build material and transport film in a singlecontainer. The invention provides a desk top modeler that can makebuilds that require less post-build cleaning and curing and can producea fully reacted, tack-free build. The invention also provides severalsubassemblies that can be adapted individually for use in connectionwith other solid imaging apparatus and methods.

The foregoing and other advantages and features of the invention and themanner in which the same are accomplished will be more readily apparentupon consideration of the following detailed description of theinvention taken in conjunction with the accompanying drawings, whichillustrate preferred and exemplary embodiments of a flexible transportdesk top modeler of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective, view of a housing for the apparatus of theinvention from the viewer's upper right-hand side;

FIG. 2 is a perspective view of the apparatus of the invention havingthe external housing removed and illustrating internal componentassemblies in relation mounted on internal supporting frame components;

FIG. 2A is a perspective view of the apparatus of FIG. 2 rotatedcounterclockwise to provide a front view from the viewer's upperleft-hand side;

FIG. 3 is a perspective view of an alternative apparatus of theinvention to that of FIG. 2;

FIG. 4 is a perspective view of one embodiment of a cartridge of theinvention from the right rear and showing a locking mechanism;

FIG. 4A is a perspective view of the cartridge of FIG. 4 illustratingopening of the lock;

FIG. 5 is a rear plan view of the cartridge of FIG. 4;

FIG. 6 is a rear plan view of the cartridge of FIG. 4 illustrating inaddition rotation of a rotary valve to a flow position for buildmaterial and of couplings for application of build material to thetransport surface and retraction of the transport surface;

FIGS. 7 and 8 are partial plan views from the side of the rear wall ofthe cartridge of FIG. 4;

FIG. 9 is a sectional view of the rear wall of the cartridge of FIG. 4taken from underneath the spring bracket lock and viewing upwardly;

FIG. 10 is a front plan view of an alternative cartridge and lockingmechanism to that of FIG. 4;

FIG. 11 is a partial perspective view of a portion of the apparatus ofFIG. 10;

FIG. 12 is a partial perspective view of a rear portion of the apparatusof FIG. 10;

FIG. 13 is a perspective view of a portion of the apparatus illustratedin FIG. 12;

FIGS. 14 and 15 are sequence sectional plan views of the relation of theapparatus illustrated in FIG. 12 to additional portion of the apparatus;

FIG. 16 is a partial perspective view of the underside of a cartridge ofthe invention from the lower right;

FIG. 17 is a partial perspective view of a frame into which selectedembodiments of the cartridge of the invention may be inserted;

FIG. 18 is a partial side sectional view of the apparatus of FIG. 17;

FIG. 19 is an overhead partial perspective view of the floor of a frame,illustrated in FIG. 3, supporting the cartridge and illustrating anarticulating housing for a seal for engaging the cartridge floor andsecuring a pneumatic connection to the cartridge;

FIG. 20 is an underside partial perspective view of the articulatingseal housing illustrated in FIG. 19 taken from below the floor of thecartridge frame illustrated in FIG. 3 and illustrating leaf springsattached to the underside of the cartridge frame engaging the housing;

FIGS. 21 and 22 are partial plan views from the side of the cartridgeframe floor, leaf spring and articulating seal housing of FIG. 20illustrating in FIG. 21 the seal housing as it engages the cartridge oninsertion into the frame and in FIG. 22 the housing in position when thecartridge is fully inserted;

FIG. 23 is an overhead partial perspective view of the cartridge of FIG.4 with the cover removed and illustrating the intra-layer cleaningassembly, a contact roller assembly for retracting the transportsurface, and a coating roller assembly for applying build material tothe transport surface;

FIG. 24 is a view similar to that of FIG. 23 illustrating theintra-layer cleaning assembly and transport surface partially extendedfrom the cartridge;

FIG. 25 is a perspective view of an isolated component of FIGS. 23 and24;

FIGS. 26 and 27 are partial sectional side-plan view of an upper sectionof the cartridge of FIGS. 23 and 24, respectively;

FIGS. 28 and 29 are transverse sectional plan sequence views through thecartridge of FIG. 10 illustrating, respectively, extension of thetransport surface in the absence of coating with build material andretraction of the transport surface with scraping and recovery of buildmaterial from the transport surface;

FIGS. 30 and 30A are perspective views of a chassis assembly of theinvention;

FIGS. 31 and 32 are overhead left-hand sequence views of the undersideof a section of the cartridge of FIG. 25 taken from the front of thecartridge as the cartridge faces the front of the apparatus of FIG. 2and illustrating a rotary valve for controlling flow of build materialin an open position in FIG. 31 and rotated to a closed position in FIG.32;

FIGS. 33 and 34 are sectional plan sequence views taken along lines33-33 of FIG. 31 and 34-34 of FIG. 32, respectively;

FIG. 35 is a partially broken away, partially sectional view of thelower section of the cartridge of FIG. 4 illustrating a main buildmaterial reservoir, a diaphragm pump for build material, and a conduitsupply to a tray reservoir for the build material located above thelower section;

FIG. 36 is a perspective view of a diaphragm pump and reed valve forcontrolling build material flow to the pump;

FIG. 37 is an overhead right-hand perspective view of one embodiment ofthe intra-layer cleaning assembly taken from the cartridge side of theassembly;

FIG. 37A is partial transverse sectional view of the intra-layercleaning assembly of FIG. 37 illustrating in addition a section througha build as excess uncured build material is removed and collected forreuse;

FIG. 38 is an overhead perspective view of another embodiment of theintra-layer cleaning assembly shown extending from a cartridge and overan image plane;

FIGS. 38A and 38B are partial perspective views of a portion of theapparatus of FIG. 38;

FIG. 39 is an overhead perspective view of yet another embodiment of theintra-layer cleaning assembly of the invention shown extending with thetransport film;

FIGS. 40 through 40E are a sequence of sectional and plan viewsillustrating the sealing of the intra-layer cleaning assembly of FIG. 39in a cartridge of the invention;

FIGS. 40F and 40G schematically illustrate the intra-layer cleaningassembly of FIGS. 40 through 40E in positions for clearing buildmaterial from a component of the assembly and for clearing buildmaterial from the assembly itself, respectively;

FIG. 41 is a partial overhead perspective view from the side oppositethe intra-layer cleaning assembly of an assembly for securing theintra-layer cleaning assembly for extension of the transport film;

FIG. 42 is view similar to that of FIG. 41 rotated counter clockwise toillustrate securing of the intra-layer cleaning assembly to the tractormotor assembly;

FIG. 43 is a front plan view of a lever arm of the motor assembly takenfrom FIG. 41 in an upright, non-secured position for securing theintra-layer cleaning assembly;

FIG. 44 is a side sectional plan view of the lever arm of FIG. 43 takenalong line 44-44 of FIG. 43;

FIG. 45 is a front plan view similar to that of FIG. 43 illustrating thelever arm rotated to a secured position;

FIG. 46 is a side sectional plan view of the lever arm of FIG. 45 takenalong line 46-46 of FIG. 45;

FIG. 47 is an overhead plan view of an alternative embodiment of theinvention corresponding to FIG. 3;

FIG. 48 is a partial perspective of a portion of the apparatus of theinvention associated with the embodiments of FIGS. 3 and 47;

FIG. 49 is an overhead perspective view of an isolated image plane,image plane supporting frame, and cartridge of the apparatus of theinvention, taken from FIG. 2, and viewed from the upper left-hand side;

FIG. 49A is a view similar to that of FIG. 49, illustrating in additionextending the intra-layer cleaning assembly and the attached transportfilm coated with build material;

FIG. 49B is a view similar to that of FIGS. 49 and 49A, illustrating inaddition the fully extended intra-layer cleaning assembly, fullyextended coated transport film, and imaging from the underside of alayer of build material on the film;

FIG. 49C is a view similar to that of FIG. 49B, illustrating in additiona build in contact with the build material on the film and held in placeby a build platform assembly;

FIG. 49D is a perspective view similar to that of FIG. 5, illustratingretracting the transport film and intra-layer cleaning assembly into thecartridge after imaging of the build material layer on the transportfilm;

FIGS. 50, 50A, and 50B are front plan sequence views of the image plane,image plane support frame, transport film, and intra-layer cleaningassembly illustrating extension from the cartridge and over the imageplane;

FIGS. 51 and 52 are front plan sequence views similar to that of FIGS.50, 50A, and 50B and starting from the FIG. 50B position illustrating inaddition in FIG. 51 a build and platform assembly engaging the buildmaterial on the transport film for curing and in FIG. 52, the buildrising from the image plane for intra-layer cleaning by the intra-layercleaning assembly;

FIG. 53 is a partial perspective view illustrating one end of thetransport film mounted in a bracket;

FIG. 54 is a sectional plan view taken along line 54-54 of FIG. 53;

FIG. 55 is an overhead right-hand front-perspective view of the imageplane and image plane supporting frame;

FIG. 55A is a partial overhead perspective view of one corner of theimage plane supporting frame illustrating a vacuum channel;

FIGS. 55B and 55C are schematic and sectional partial-plan sequenceviews illustrating placement of the radiation transparent image plane inthe supporting frame for the image plane;

FIG. 55D is a partial right-hand perspective view from underneath andfrom the front of the apparatus as illustrated in FIG. 2, illustratingmounting of one end of the transport film in a bracket and attachment tothe intra-layer cleaning assembly of the invention;

FIG. 56 is a partial perspective view from the right front of theapparatus of FIG. 2 illustrating a build platform being inserted into abuild platform assembly, including in addition to the build platform, asupporting frame, a pair of independent elevator brackets, and a vacuumsupply for securely attaching the build platform to the assembly;

FIG. 56A is a plan view in partial section from the underside of thebuild platform assembly of FIG. 56 with the build platform insertedillustrating the raised discontinuous structure of the underside of thebuild platform for supporting a build and a section along line 56A-56Aof FIG. 56C illustrating a recess in the build platform into which fitsa section of the build platform supporting frame;

FIG. 56B is a left-hand underside perspective view of the build platformof FIG. 56;

FIG. 56C is a front plan view of build platform assembly of FIG. 56illustrating the build platform secured to the supporting frame;

FIGS. 57 and 57A are perspective views of the upper and lower surfaces,respectively, of an alternative embodiment of a build pad of theinvention;

FIG. 58 is a perspective view if an alternative build platform of theinvention;

FIG. 59 is a sectional plan view of a build and build platform of theinvention as it approaches the image plane;

FIG. 60 is a plan view of the build pad and support structure for abuild;

FIG. 61 is an exploded perspective view of an elevator assembly of theinvention;

FIGS. 62 and 63 are sectional plan views of a build and build platformof the invention upon entering the image plane and lifted from the imageplane, respectively;

FIGS. 64, 64A, and 64B are exploded perspective views of an imagerassembly and alignment fixture of the invention;

FIGS. 65 and 66 are schematic plan sequence views, the plan views beingtaken from the right side of the apparatus by rotating the apparatus ofFIG. 2 counterclockwise, illustrating a digital light processing (“DLP”)imager illuminating the underside of the radiation-transparent imageplane via a mirror assembly for folding the image in FIG. 65 and then inFIG. 66 retraction of one mirror for illumination of the image plane bya high-intensity UV assembly for post-image curing;

FIGS. 67 and 67A are overhead perspective sequence views from theviewer's left-hand side, viewing the front of the apparatus of FIG. 2,of the image plane in partial section and the frame for the image planemounted atop a UV assembly and illustrating a retractable mirror in FIG.67 and retraction of the mirror in FIG. 67A for illumination of theimage plane by the UV assembly;

FIG. 67B is a partial perspective view from inside the right-hand frontcorner of the UV assembly of FIG. 67A illustrating the retracted mirrorof FIG. 67A from underneath the image plane and facing the left-mostrubber roller wheel, which rotates against a friction surface to retractand extend the mirror;

FIG. 68 is a sectional schematic partial side plan view taken from FIG.67B illustrating the toothed rubber roller wheel, drive motor M,friction surface, mirror-supporting frame, and mirror retraction track;

FIG. 69 is a perspective view of a halo assembly of the invention forsecondary cure UV exposure of the sides of the build; and

FIG. 70 is a perspective view of a hood assembly of the invention forsecondary cure UV exposure through the build platform.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DETAILED DESCRIPTION

This invention can best be understood with reference to specificembodiments that are illustrated in the drawings and the variationsdescribed herein below. While the invention will be so described, itshould be recognized that the invention is not intended to be limited tothe embodiments illustrated in the drawings. On the contrary, theinvention includes all alternatives, modifications, and equivalents thatmay be included within the scope and spirit of the invention as definedby the appended claims.

FIG. 1 illustrates in a perspective view generally at 99 one embodimentof a housing for a desk top modeler of the invention. Housing 99includes right and left hand hinged doors 102, 104. The hinge for door102 can be viewed at 106. Door 102 is provided with handles 110, 114 anddoor 104 is provided with handles 112, 116 on the door face and top,respectively. It should be recognized that a wide variety of sucharrangements profitably can be used, a primary requirement being thatthe housing, or at least the conditions under which the apparatus isused, does not permit light to enter during operation. A track 118 isprovided on the doors, which track can contain signal lights, such ascontroller responsive light emitting diodes (“LED's”) for indicatingvarious operational stages of the apparatus, such as when a build is inprogress or when a build is complete, or when a door is locked onunlocked to provide access.

Housing 99 also includes left and right exterior side panels 122, 124and a top panel 126. An electrical control panel 128 is provided in therear of the apparatus. The housing components typically are preparedfrom sheet metal, including stainless steel, although other materialsshould also be useful. One of numerous vents for forced air cooling isprovided in right side panel 122 at 130. Vent 130 is one of two forcedair vents for the imager for the apparatus, which may be viewed insubsequent figures.

FIGS. 2 and 2A illustrate generally at 100, and FIG. 3 illustratesgenerally at 101, perspective views of alternative embodiments of asolid imaging apparatus of the invention having selected housingcomponents removed for viewing the interior. The views of FIGS. 2 and 3are from the front of the apparatus from the viewer's upper right-handside. The view of FIG. 2A is that of FIG. 2 rotated counterclockwise toprovide a front view from the viewer's upper left-hand side. Theseapparatuses are desk-top modelers for flexible imaging and the views ofthe interiors illustrate internal component assemblies in relationmounted on supporting frame components. It should be recognized thatwhile a flexible transport desk-top modeler is described and illustratedherein, the invention incorporates several features, components, andsubassemblies having applicability apart from the desk top modeler asillustrated. This detailed description presents illustrations anddescriptions of several subassemblies and additional aspects of theinvention and various modifications and changes may be made withoutdeparting from the scope of the invention as set forth in the appendedclaims.

It should also be understood that the desk top modelers 100, 101 arecomputer controlled devices and that an operator's computer controlstation communicatingly connects to the modeler via an electrical panelfor controlling its operation and that of the various subassemblies,neither of which is illustrated here.

FIGS. 2, 2A, and 3 illustrate several primary operational componentsubassemblies of embodiments of the modeler and these are numbered inFIGS. 2, 2A and 3 as subassemblies for convenience and ready location.It should be recognized that the individual component numbered in FIGS.2, 2A, and 3 may be only one of several components of the subassembly,in which case that component may bear a different number in laterdrawings illustrating the subassembly in detail.

The subassemblies illustrated in FIGS. 2 and 2A include:

1) external frame components, including support columns 132, a floor134, upper and lower horizontal supports 136 and 137, an upper cap 138,and a slotted rear wall 139 on which is mounted an electrical panel,which is not shown;

2) internal frame components for subassemblies of the invention,including vertical left and right walls 140 and 142 extending generallyin a front-to-rear and ceiling to floor direction with several cut-outportions for forced air circulation and electrical passages and forsupporting several subassemblies, and vertical wall 143 extendinggenerally in a side-to-side direction that supports an imager 1100 (FIG.2A);

3) a self-contained removable and replaceable cartridge assembly 200′providing a source of build material, an intra-layer cleaning assembly300, and an extendible and retractable transport film 400 fortransporting the build material, the cartridge assembly being mountedinto a frame, including motor 524 for retracting the intra-layercleaning assembly 300 and transport surface 400 and motor 526 forapplying build material to the transport surface 400;

4) an image plane assembly 600 across which transport surface 400extends to transmit build material for imaging and through which solidimaging and post-curing radiation reach a build surface;

5) a build platform and frame assembly 700;

6) an elevator assembly including a pair of left and right independentlyoperated elevator arms 900 and 1000 for raising and lowering the buildplatform assembly 700 with respect to the image plane assembly 600;

7) an imager assembly 1100 for supplying radiation to the build forconstructing the build and which is mounted to vertical internalstructural wall 143 via a tongue and groove fit in a mounting bracket1102;

8) one of multiple vent assemblies 1300 for the imager 1100, one on theright in FIG. 1 and one on the left in FIG. 2;

9) a mirror box 1400, 1402 (FIGS. 65, 66, and 67), formed by a UV shield1400 and walls 1402 and containing a pair of mirrors and including inshield 1400 UV reference photo diodes 1401, the mirrors transmitting theimage from the imager to the image plane, and including in FIG. 2A amotor 1425 for extending and retracting one of the mirrors;

10) a high-intensity ultra-violet light source, UV box 1500, for postcuring the build layer-by-layer; and

11) one embodiment of multiple vent assemblies 1600 for the UV lightsource 1500.

The subassemblies or portions of subassemblies illustrated in theembodiment of FIG. 3 include:

1) a floor 134′, which is an external frame component, the remainder ofthe external frame having been removed for clarity;

2) a vertical wall 143′, which is an internal frame component extendinggenerally in a side-to-side direction that supports an imager 1100 (FIG.2), the remainder of the internal frame having been removed for clarity;

3) a self-contained removable and replaceable cartridge assembly 200″providing a source of build material, an intra-layer cleaning assembly(not shown in this view), and an extendible and retractable transportfilm (not shown in this view) for transporting the build material, thecartridge assembly being mounted into a frame 500′, including motor 524″for retracting the intra-layer cleaning assembly and transport surfaceand motor 526″ for applying build material to the transport surface;

4) an image plane assembly 600′ across which the transport surfaceextends to transmit build material for imaging and through which solidimaging and post-curing radiation reach a build surface;

5) a build platform and frame assembly 700′;

6) an elevator assembly including a pair of left and right independentlyoperated elevator arms 900 and 1000 for raising and lowering the buildplatform assembly 700′ with respect to the image plane assembly 600′;

7) an imager assembly 1100 for supplying radiation to the build forconstructing the build and which is mounted to vertical internalstructural wall 143′ via a tongue and groove fit in a mounting bracket1102;

8) one of multiple vent assemblies 1300 for the imager 1100, one on theright in FIG. 1B and one on the left (not shown, and similar to that ofFIG. 2 at 1300;

9) a fixed mirror assembly 1399 for transmitting the image from theimager to the image plane, the mirrors oriented with respect to theimage plane; and

10) ultra-violet light sources, a halo assembly 1500′ mounted to anelevator 1501′ and a hood assembly 1500″ for post-curing the buildlayer-by-layer.

The build materials described below in connection with the practice ofthe invention respond to actinic radiation in the visible andultraviolet regions. The term “solid imaging radiation” is used hereinto refer to any actinic radiation which causes a photocurable liquid toreact to produce a solid, whether a visible or UV source or othersource. The imagers described below provide solid imaging radiation forinitially curing the build material image onto a build surface in boththe visible an ultraviolet ranges. These imagers have been modified toprovide both visible and UV light, within the limits of the device to doso, including a modified commercial digital light processing projector(“DLP” projector) for which specific embodiments are illustrated anddiscussed. The modified DLP projector used for the imager produces morevisible than UV light and the build materials can be tailored to receivethe maximum benefit from the particular projector used. It should berecognized that imagers can also be created based on UV sources or othersources of actinic solid imaging radiation that do not include visiblelight and build materials tailored for these sources.

The actinic light sources for solid imaging radiation used for postcuring operations, to provide a more fully or completely reacted buildafter the intial image, do not typically provide visible light, but onlyultraviolet. These UV sources are also described in more detail below.

Turning now to a discussion of the cartridge, FIGS. 4 and 4A illustrategenerally at 200 one embodiment of the cartridge of the invention in aperspective view from the rear. The cartridge includes flexiblecouplings 224 and 226, which may be, for example, ball drive and hexshaft couplings, extending from spaces between the lid 204 and uppersection 220 for engaging corresponding motors 524 and 526 mounted on thecartridge frame (FIGS. 2 and 2A). The couplings and motors cooperate toretract a cleaning assembly 300 and transport surface 400 and (FIGS. 2and 2A) into the cartridge and to coat the transport surface with freshbuild material. The end of a rotary valve 203 for controlling buildmaterial flow in the cartridge interior extends exteriorly of thecartridge from an orifice adjacent the top of lower section 250, wherethe build material is stored. Valve 203 is shown in an upright andclosed position, secured by spring locking plate 205.

The cartridge 200″ illustrated in the embodiment of FIG. 3 is ofsomewhat similar design in its interaction of ball hex drive couplingswith motors 524″ and 526″ and has similar internal components, asdescribed further below with respect to the cartridge interior.Cartridge 200″ does not include a cleaning assembly 300 and operatesinstead in a manner described below to use the transport surface toremove excess uncured build material from the build surface. Cartridge200″ is also illustrated with an optional handle, which is not presentin the cartridge 200 of FIGS. 4 and 4A.

As shown in FIGS. 4 and 4A, the cartridge in one embodiment may includea spring locking plate 205 having a fitting 207 that engages valve 203to preclude rotation of the valve to a build material flow positionuntil the plate is disengaged. The plate has corner fittings 209 and 211that engage toothed couplings 224 and 226, respectively, to precludeeither retraction of the transport film or coating until the springlocking plate is disengaged. The spring locking plate is disengaged bypushing downwardly on the plate, as illustrated by the directionalarrows in FIG. 4A.

FIGS. 5 and 6 are sequence plan views of the rear of the cartridge andillustrate disengagement of the locking plate, which is biased to alocked position in engagement with couplings 224, 226 and valve 205 bytorsion springs 206 mounted on standoffs extending from the cartridgehousing.

FIGS. 7, 8 and 9 provide more detailed side views of the locking plate,illustrating its interaction with the cartridge activating and unlockingelement 505 on the cartridge frame. Member 505 on the frame engagescorresponding sloped surface 205 on the locking plate to push thelocking plate downward as the cartridge is inserted fully into thecartridge frame. By the time the cartridge is fully inserted, the rotaryvalve and couplings on the cartridge are fully rotational. This featurecan also be used in connection with the cartridge embodiment of FIG. 3and provides for secure transport and storage of the cartridge untilready for use, without spilling build material. The cartridge is fullysealed against light intrusion to protect the build material, as well,for both storage and when in use in the apparatus of the invention.

FIGS. 10 and 11 illustrate an alternative way to lock the rotary valve203 (FIG. 11) from the front of the cartridge rather than the rear. Ahandle 1900 mounted on a snap 262 at the end of the rotary valve engagesa toothed member 1901 that precludes the valve from turning until anoperator positively grasps the handle and lifts it to bypass the teethto turn the valve to an open position, thus eliminating the springbracket locking member of the embodiments discussed above.

FIGS. 10 and 11 also illustrate a housing 202′ having the same basicfeatures of a lid and upper and lower sections, 250′, 220′, and 204′,respectively, corresponding to those of FIGS. 4 and 4A at 250, 220, and204, and having a more rounded and pleasing appearance. These featuresare all discussed in detail below in connection with the cartridgeinterior and operation of the cartridge.

FIGS. 12 through 15 illustrate an alternative arrangement for mountingball hex flexible couplings and securing the cartridge against operationuntil inserted fully into the frame 500, 500′ (FIGS. 2 and 3) for thecartridge on the desk top modeler. Brackets 224″ and 226″ in the upperhousing section 220′ and corresponding brackets in the lower housinghave internal notches 1550 corresponding to teeth 1550′ (FIG. 13) on thehex portion 224′ and 226′ of the flexible coupling contained in thecartridge. The hex coupling is biased by a spring (1726, 1826 in FIG.14) to have the teeth 1550′ inserted into the corresponding notches 1550to preclude the axes 1717, 1728 of the contact roller and coatingroller, respectively, from turning. When the corresponding ball 524′,526′ inserts into the hex coupling, the hex coupling is pushed out ofcontact with the notches against the spring and is released for rotation(FIG. 15). One advantage of this embodiment is that the hex couplingsare internal to the cartridge housing.

FIG. 16 illustrates the bottom 250 of the cartridge housing from a lowerright-hand perspective from the rear and illustrates one embodiment forconnection of the cartridge to an air source at internal air flow path1650 for operating a diaphragm pump for circulating build materialwithin the cartridge and for conveying build material to the transportsurface. The diaphragm pump is located at 1350 in a chamber provided andits features and operation are described in detail below.

FIGS. 17 and 18 illustrate air supply to the diaphragm pump through theair flow path 1650 of FIG. 16. A corresponding air probe 1650′ connectedto an air pump in the desk top modeler, which generally is located inthe electrical panel 128 (FIG. 1), inserts into the path 1650 when thecartridge is inserted into its frame 500 (FIG. 17; 550′ as illustratedin FIG. 3). The air flow path connects through orifice 1351 with thediaphragm pump chamber 278 in the lower portion of the cartridge housing250 (FIG. 18; 250′ in FIG. 10).

The frame 500 (500′ in FIG. 3) is well illustrated in FIG. 17 for theembodiment having an air probe connection to the diaphragm pump. The airprobe inserts through orifices in the rear wall of the frame and framefloor 530 and is secured in the floor of the frame for engagement of theair flow path 1650 (FIG. 16) when the cartridge is inserted into theframe. The cartridge may also include a radio frequency identificationtag on the housing mounted beneath the flexible drive motor couplingscorresponding to a reader 545 on the frame to identify the buildmaterial and to ensure compatibility.

FIGS. 19 through 22 illustrate another embodiment of an air supply forthe diaphragm pump. A flexible air supply conduit 1653 (FIGS. 19 and 20)receives air supply from an air source (not shown) contained in anelectronics component panel 128 (FIG. 1) at the back of the modeler. Airsupply conduit 1653 travels below the floor 530 of the frame 500 (FIG.17; 500′ in FIG. 3). When an operator inserts a cartridge into thecartridge frame, the cartridge engages the spring-biased ramped surface1652 of a lever arm actuator 1654 located in the frame floor to push theair supply conduit into communication with an air receiving orifice 1352on the diaphragm pump (FIG. 36) (FIGS. 21 and 22). Springs 1655 mountedon the underside of the frame floor supporting the cartridge keep theair conduit, which travels through the actuator 1654, in air supplyingcontact with the cartridge (FIG. 22).

Proceeding now to a detailed discussion of the interior of thecartridge, the reader should recognize that while the internalcomponents are discussed with reference to the housing embodiment ofFIG. 4, the features are generally similar to the internal components ofFIGS. 3 and 10, with the exceptions that the embodiment of FIG. 3 doesnot include a separate cleaning assembly and alternatives are presentedbelow for the cleaning assembly.

FIGS. 23 and 24 illustrate the cartridge housing 202 with the lid 204removed and exposing the internal components in the upper section 220 ofthe housing, including the intra-layer cleaning assembly having a rollerbrush 314 rotatably mounted in a housing 320 for removal of excessuncured build material. Excess uncured build material can be removed byspinning the brush for cleaning or using a squeeze roller to recoverexcess uncured build material for reuse, as explained in detail below inconnection with detailed drawings of the cleaning assembly. The excessuncured build material removed from the build surface, along with excessuncured build material remaining on the film, can be passed into a lowersection 250 of the cartridge and through a filter 267 (FIGS. 28 and 29)to remove particles for reuse until the cartridge is spent and replaced.

A contact roller 230 contacts the film for extension and retraction andis rotatingly coupled to coupling 224 for driven retraction of the filmby motor 524 (FIGS. 2 and 3). Coating gravure roller 240 applies buildmaterial to the film. Coating roller 240 is activated for coating thefilm by a rod 245 driven by coupling 226 connected to motor 526 (FIGS. 2and 3). A tray reservoir, not seen in this view, is disposed just belowthe coating roller to apply a thickness of build material 410 to thecoating roller. As illustrated in FIG. 23, the film is fully retractedand the cleaning assembly is fully retracted into the housing. Asillustrated in FIG. 24, the film is being extended and coated.

FIG. 25 presents a detailed view of the isolated coating roller toillustrate control of the thickness of build material applied to thefilm. As shown in FIG. 25, the thickness of build material is determinedby the distance between the contact roller 230 and hard plastic stopdiscs on the ends of the coating roller, 242′ and 243′. Adjacent ends242 and 243 are made of the same elastomeric material as the coatingroller 240, typically a silicone rubber, but are of a slightly largerdiameter for an interference fit with the film on the contact roller,acting as drive tires to rotate the coating roller against the extensionof the film. The ends 242 and 243 are resilient and compress to thediameter of the hard plastic stops 242′ and 243′ to control thethickness of the build material applied to the film.

Sectional views of FIGS. 26 and 27 further illustrate how the coatingroller engages the contact roller. Actuator rod 245 is connected as alever to tray reservoir 246 containing build material 410 and coatingroller 240. As shown in FIG. 26, unless the actuator rod 245 isactivated, the coating roller does not contact the film and no buildmaterial can be applied. When the rod is pushed forward, as in FIG. 27,the reservoir and coating roller engage the film 400 on the contactroller 230 to coat the film as the film is extended.

The layer of build material applied to the film should have asubstantially uniform depth as applied across the film, although thatdepth can vary in each layer between certain upper and lower limits. Thethickness of build material on the transport film should be at least asthick as the layer of the corresponding cross-section being formedduring the build process. If the layer of build material applied to thefilm is too thick, then the build cannot displace sufficient buildmaterial to form the part layer with the desired layer thickness. If thelayer of build material applied to the film is too thin, then thecross-section formed on the build will be less than the desiredthickness, potentially ruining the build. Generally speaking, the depthof the layer applied to the film will range from about 0.0045 to 0.0055inches thick. In the production of hearing aid shells, thinner layers offrom about 0.002 to 0.0025 inches thick are typical.

The thickness of the layer of build material applied to the build duringthe build process contributes to the resolution of the build objectproduced. The depth of the individual layers may vary fromlayer-to-layer depending upon the part being built or the stage ofproduction. Initial layers of build material for support structuressometimes are somewhat thicker while layers for delicate thin buildstructures may be somewhat thinner.

Two primary factors determine thickness of the build material layer asapplied to the build: the thickness of the transport film and thethickness of the initial and subsequent layers applied to the transportfilm during the build process. The film normally is slightly thickerthan the build material layer thickness, typically by from about 0.0005to 0.0015 inch. Film thickness can vary somewhat across its span,although a substantially uniform film thickness is desirable.

Turning now to a discussion of the internal components of the cartridgeas these components are arranged in the three sections of the cartridgehousing, FIGS. 28 and 29 illustrate sectional views through thecartridge assembly 200 to show the film extending (FIG. 28) andretracted and stored (FIG. 29). While a cleaning assembly 300 is shown,it should be recognized that this feature is absent from the embodimentof FIG. 3 and as further illustrated below, and that the operation andlocation of the remaining components is substantially the same.

FIGS. 28 and 29 show the intra-layer cleaning assembly 300 attached tothe film 400 in the lid 204 of the cartridge housing. FIG. 28illustrates the film extending from an opening in the lid 204 adjacentthe upper section 220 of the housing, and seals 280 that are formedbetween the lid and the upper section of the cartridge housing andbetween the upper and lower sections of the housing. The seals,including that for the fully retracted intra-layer cleaning assembly,preclude loss of build material or contamination by light, including UVlight.

A gravure reservoir 246 in the upper section of the cartridge housingreceives build material 410 from a storage reservoir 290 in the lowersection of the housing, from which the build material is conveyed tocoating roller 242 for coating the transport film in the mannerdescribed above in connection with FIGS. 24 through 27.

The lower housing includes a first wetted chamber 290, which is thereservoir for build material, separated by an internal wall 291 defininga second dry chamber for accommodating chassis legs 276 and storing theretracted film when the cartridge is assembled, and a third chamber 278for a diaphragm pump 1350 (FIG. 36) for conveying build material fromthe reservoir 290 to the upper section 220 for application to thetransport film 400 by the coating roller 242. When assembled, thechassis legs 276 extend through the upper section of the housing intothe dry chamber in the lower housing, while the coating and contactrollers 242, 230 respectively, are located in the upper housing. Theentire chassis is shown in perspective in FIGS. 30 and 30A generally at275.

FIGS. 28 and 29 also show a scraper 260 defined by a sharp upper edge ofinternal wall 291 of the cartridge housing. The scraper contacts thefilm when it is being retracted and removes resin from the film so thata clean film will result.

The floor 221 of the upper section of the housing 220 directs excessuncured build material removed from the film and obtained from theintra-layer cleaning assembly through elastomeric fittings 252 and 254(FIG. 31) to the open rotary valve 203, which passes the recovered buildmaterial through to the build material reservoir 290 of the lowersection of the cartridge.

The build material is drawn through a filter 267 to remove solids by adiaphragm pump located in the lower section of the housing in a thirdpump chamber at 278 beneath the build material reservoir to removesolids. The diaphragm pump continuously circulates the build materialduring use to maintain homogeneity.

FIGS. 30 and 30A show the film chassis 275 in perspective upon which aremounted the contact roller 230, the coating roller 242, and the gravurereservoir 246 (FIGS. 28 and 29). The chassis has elongated legs 276 andan elongate longitudinal slot 276′ in each leg providing a track for afollower rod 265 about which the film travels to its terminationadjacent the contact roller. The follower rod provides tension to thefilm when it is extending or retracting. The retractor motor 524 (FIG.2) causes take-up straps 277 located on the exterior of each leg 276 andattached to an idler rod 279 to pull the follower rod 265 down the slotto retract the film.

FIGS. 31 through 34 illustrate operation of the rotary valve 203,viewing the valve from the underside, looking upward to the bottom ofthe upper section 220 of the cartridge. The ends of valve 203 protrudethrough openings in the lower housing section 250 (FIG. 4; 250′ in FIG.10, one end 262 extending to engage a valve handle (see FIGS. 2, 3, andcomponent 1900 in FIG. 10) and the opposite end 264 extending, in theembodiment of FIG. 4, to engage spring locking bracket 205 (no lockingbracket is needed in the embodiment of FIG. 10, which relies instead ona locking valve handle).

The valve 203 in its open position establishes flow communication withthe build material reservoir in the lower section (not shown in thisview) for return of unused build material. In its closed position, thevalve seals against flow of build material into or out of the lowerwetted section. The unused build material comes both from the build, byremoval with the cleaning assembly 300 or film, and from the retractedfilm itself on which unused build material remains. The unused buildmaterial travels via through-openings 253 to elastomeric fittings 252,254 fitted into a floor 256 between the valve and the upper section ofthe cartridge.

A conduit 258 is provided for supplying build material from thereservoir to the gravure tray 246 in the upper section (not shown inthis view). The valve is shown in flow communication in FIGS. 31 and 33.When the valve is in a closed position, as in FIGS. 32 and 34, theconduit is pinched against supporting member 260, which extends from theupper section underside, and seals against elastomeric members 252 and254 to preclude flow either to or from the reservoir in the lowersection.

It should be noted that the cartridge assembly is filled with buildmaterial from the top, with the lid removed, through opening 253.Alternatively, an orifice 269 could be provided, as illustrated, throughwhich the build material may be filled and then sealed with a cap.

FIGS. 35 and 36 illustrate a diaphragm pump 1350 in greater detail. Thediaphragm pump pumps the build material 410 (FIGS. 28 and 29) from thefirst wetted chamber 290 of the housing 200 to the coating reservoir246. The pump resides in a third chamber 278 beneath the build materialreservoir (first wetted chamber 290) so as to use gravity to make thebuild material flow to the pump and thus ensure that all build materialcontained in the wetted section can be consumed before the cartridge isreplaced or discarded.

The diaphragm pump has an air inlet 1352 (FIG. 36) for actuating thediaphragm retract 1354 to push build material in the pump through theconduit 258 and into the gravure reservoir 246. When air is off, theweight of the build material pushes through a slot in the bottom of thewetted chamber (not shown) against reed valve 1355 to fill the pumpcavity with build material and flatten the diaphragm against the pumpcover. The reed valve allows build material to flow from the wettedchamber to the pump but does not allow flow back into the wettedchamber. Likewise, a ball check valve 1356 provided in the buildmaterial outlet in the conduit to the coating reservoir allows flow fromthe pump through the conduit to the coating reservoir but prevents flowback into the pump.

To activate the diaphragm for pumping, air is supplied though orifice1352 and strikes the diaphragm 1354 to push the diaphragm upward and toforce the build material through the build material conduit 258 to thecoating assembly reservoir 246 in the upper section. Pulsing the air onand off continually fills and empties the pump cavity to convey buildmaterial to the reservoir.

When the cartridge is delivered to a user, the diaphragm pump would befilled with build material and the rotary valve handle would be in theclosed position. The rotary valve openings for build material flow wouldbe turned to the side, pinching the flow conduit and precluding flowthrough the conduit to the upper section of the housing. The valvehandle is ineffective to turn the rotary valve until either unlocked(FIG. 10), or the cartridge assembly is fully inserted into the desk topmodeler and the spring clip engages the fitting on the rear wall of thecartridge frame (FIG. 4A). These features, along with other sealingfeatures relating to the cleaning assembly and joinder of the housingsections, discussed below, substantially reduce the possibility of buildmaterial leakage from the cartridge.

When rotated to the off position, the valve pinches the conduit from thediaphragm pump to the coating reservoir and precludes fluid entering thereservoir, even if it could negotiate the inactive diaphragm pump's reedvalve and check valve, which is highly unlikely. When actuated, thediaphragm pump is supplied with air, the rotary valve releases the fluidconduit, and the valve provides a recycling passageway from the scraperand filter to the main reservoir. This recycling passageway is closeduntil the valve is turned when the cartridge is fully inserted into themodeler.

Turning now to a discussion of the extension of the film and intra-layercleaning assembly from the cartridge, FIGS. 37 through 46 illustratevarious intra-layer cleaning assemblies and FIGS. 47 and 47A illustrateembodiments including that of the apparatus of FIG. 3 in which nocleaning assembly is attached to the film.

FIGS. 37 and 37A illustrate the components and operation of oneembodiment of the intra-layer cleaning assembly. Brush roller 314 isaxially mounted for rotation within housing 320 about axis 315. Axis 315is rotatingly connected to drive motor 312 through motor driven arm 310.Motor driven arm 310 is separately driven, in a manner described below,to extend the cleaning assembly and film.

A suitable roller brush 314 includes synthetic mohair brushes used forrollers for applying adhesives or paint. These roller brushes have asoft pile and short fibers of about 3/16ths inch length that do notdamage the build and readily remove uncured build material.

The roller brush is extended with the film and, upon retraction in thedirection of the arrow of FIG. 37A, contacts the surface of the build toremove excess uncured build material. The rotating brush rotates incontact with the surface of the build at a suitable rate to removeexcess uncured build material, which normally is in the range of about360 rpm's (revolutions per minute) in a clockwise direction. In theembodiment illustrated, a squeeze roller 322 is provided for removingexcess uncured build material from the cleaning roller brush 314. Thesqueeze roller, held against the cleaning brush under the tension ofsprings 322′, continuously squeezes the fibers of the cleaning brush toremove the build material (FIG. 37A) for return to the cartridge.

The excess uncured build material travels out of the housing 320 viaopening 321 in the housing and onto the film and into the cartridge forrecovery. When the assembly returns to the cartridge, it is sealedagainst UV exposure as described below in connection with the embodimentof FIGS. 39 through 40E.

FIGS. 38 through 38B illustrate an alternative to the roller brush 314of the previous FIGS. 37 and 37A. The cleaning assembly of FIGS. 38through 38B is an oscillating linear brush 314′, oscillated on aneccentric arm 311 by a motor 312′. A leaf spring 323′ is provided toassist in securing the cleaning assembly housing 320 and oscillatinglinear brush 314′ in the cartridge 202. FIG. 38 illustrates the cleaningassembly and film extended out of the cartridge and traveling in thedirection of the arrow across the image plane 605 and frame 610 forimaging. FIGS. 38A and 38B illustrate the eccentric arm in relation tothe motor 312′ and linear brush 314′.

FIGS. 39 through 40G illustrate yet another embodiment of the cleaningassembly 300 of the invention, in which a rotating brush 314 removesexcess uncured build material as in the manner of the roller brush ofFIG. 37. Instead of using a squeeze roller to remove the excess uncuredbuild material from the brush, the embodiment of FIGS. 39 through 40spins the roller brush 314 at a high rate of about 5,000 rpm's clockwiseonce the roller brush and housing 320 are fully retracted into thecartridge housing and sealed. The roller brush spins at sufficientlyhigh rpm's, from about 3,000 to 6,000 rpm's or more, normally about5,000 pm's, to propel the excess uncured build material from the brush.The housing provides suitable splash guards 323, 323′ (FIGS. 40F and40G) for the intra-layer cleaning assembly and the opening 321′ (FIG.39) in the housing for excess uncured build material to return to thecartridge for filtration and circulation has been somewhat extended ascompared to that of FIG. 37.

The housing 320 in all of these embodiments is sealed about itsperiphery against light intrusion and to preclude build material removedfrom the brush from contaminating the area outside the cartridge. FIG.39 illustrates an elastomeric seal 320′ for sealing against lightintrusion that is actuated by a lever arm 335 as it engages a camsurface 337 on the interior of the cartridge housing. A spray shield 323(FIG. 40F) protects the seal 320′ from build material propelled from thebrush. Material is propelled from the brush at an angle of about 45degrees.

FIGS. 40A and 40B illustrate the lever arm striking the cam surface.FIGS. 40C and 40D illustrate a pivot hinge 339 actuated by the movementof the lever arm 335 across the cam to raise the seal 320′ on support341 to engage the cartridge housing to provide a light seal. It shouldbe noted that the surface of the lid 204 is tapered adjacent theentrance slot at 327 (FIG. 40F) for the cleaning assembly so that thebrush does not hit and wet the lid when the brush enters the cartridge,else the UV source would cure the material on the wetted lid. The brushis located vertically so that it touches the lid 204 once the brush isbeyond the seal 320′ and inserted fully into the cartridge. Thisarrangement mean that the brush continually removes material depositedon the lid as the brush spins, thereby ensuring the uncured buildmaterial clearing the brush does not remain on the lid.

FIGS. 40E and 40F show the cleaning assembly retracted into thecartridge housing at the high speed spinning position. When buildmaterial accumulates, the rotation speed is reduced to stop propellingbuild material and the brush is moved back and forth at least once toclear the build material propelled from the brush, which collects in theopening to the right provided by the spray shield 323′ (FIG. 40G). Asindicated with reference to FIG. 40G, the build material drips into thecartridge housing upper section to flow through the valve and into thebuild material wetted chamber in the lower section along with excessuncured build material scraped from the transport film. Pivot hinge 339engages the seal support on both sides of the “T” to raise the seal intoengagement with the cartridge housing lid portion 204 and, as shown inFIG. 40G, the seal remains against the lid as the brush housing movesleft to clear the build material propelled from the brush.

FIGS. 41 through 46 illustrate attachment of the cleaning assembly 300to the motor arm 310 (FIGS. 37 through 40). When the cartridge isinserted into the desk top modeler, the operator connects theintra-layer cleaning assembly to the motor driven arm via rotatablemechanical lever arm 316. Lever arm 316 provides a handle for rotationof the lever about an axis 330. Axis 330 extends from housing 320 andinserts into the opening in the lever arm. When the lever arm is rotatedabout the axis, an elastomeric fitting 334 in the lever arm surroundingthe axis snugs housing 320 tight to the motorized arm.

There are several factors impacting operation of the brush. Regardlessof whether a linear or rotating brush is selected, the brush shouldstroke the surface of the build a sufficient number of times to removesufficient excess uncured build material and the brush should be clearedof the build material so as not to redeposit the material on the buildsurface and so as not to contaminate the cartridge. It is desirable toprovide strokes as rapidly as possible to remove material from the buildwithout, at the same time and prior to a separate clearing step,propelling the material from the brush. The rapidity of the strokes isempirically determined. The force holding the material on the brush isproportional to the surface energy of that material on the fiberscomprising the brush. For higher surface energies, stroke speedtypically is somewhat higher than for lower surface energies.

For a rotating brush, the centrifugal force on the resin is also afunction of the angular speed in rpm's and the brush diameter. For anylon bristle brush of 1.25 inches in diameter and a build material asdescribed herein, 360 rpm has been demonstrated to be a suitablespinning speed for cleaning: not too fast to avoid propelling materialfrom the brush, and not too slow to clean inefficiently.

Multiple sweeps of the brush across the build surface are typical, inboth directions, left and right. When moving to the right, asillustrated in the figures, a rotating brush rotates clockwise. Whenmoving to the left, re-extending the cleaning assembly, a rotating brushmoves counter clockwise. Thus, the rotating brush moves counter to thedirection in which it would rotate freely simply by contacting the buildsurface.

The rate at which the brush assembly is extended and retracted acrossthe surface of the build may vary within certain limits, although afaster rate generally improves cycle time while a slower rate providesmore cleaning. A suitable combination of sweeps and rates is from about1 to 5 sweeps at from about 1 to 9 inches per second.

Brush penetration, which is the amount of interference between the tipsof the bristles and the build surface, also contributes to removingexcess uncured build material from the build surface. Higher penetrationis more effective, but too much can damage delicate build surfaces. Theembodiments illustrated contemplate about 0.080 inch of penetration.

It should be noted that the parameters discussed above vary somewhatdepending on the stage of the build. For example, when buildingsupports, clean side (vertical) walls are not as important and the brushcan be applied more slowly to sop up large amounts of uncured materialfrom the horizontal surfaces. A rotating brush can be rotated in thesame direction and at the same speed as it freely would rotate.

To clear the brush of build material inside the cartridge, the fasterthe better. The material removal rate increases with the square of therpm. Three thousand rpm clears a 1.5 inch brush and 5,000 rpm will clearthe same brush faster. A smaller brush typically will require somewhathigher rpm, and speeds above 6,000 rpm can be achieved provided themechanical rotational apparatus is sufficient. If there is a largeamount of excess material to be cleared from the brush, then the brushis retracted into the cartridge and cleared between sweeps. If there isonly a small amount of material, then the sweeps can be completed for acleaning cycle and the brush retracted and cleared at that time while aUV lamp exposure takes place.

FIGS. 47 and 48 illustrate an alternative arrangement in which noseparate cleaning assembly is provided on the transport film and thetransport film itself is used for intra-layer removal of excess uncuredbuild material. The arrangement illustrated in FIGS. 47 and 48 may beused, for example, with the embodiment of FIG. 3. FIG. 48 illustrates atractor motor 312′ for extending a transport film across the image planeassembly and a solenoid poppet 313 for releasing vacuum and shear forcesby which the transport film is held in place on the image plane 605′.The transport film is mounted to a pull strap (not shown) instead ofcleaning assembly 300 (FIG. 2) and the pull strap is secured in thetractor motor by the operator when the cartridge is installed. Since thepull strap extends across the image plane when the transport surface isfully retracted into the cartridge, this embodiment may produce buildshaving artifacts of strap image if the option of a post-curing operationis also selected. The end of the transport film 402′ to which a pullstrap is connected instead of a cleaning assembly can be viewed in FIG.47.

In operation, in the embodiment of FIGS. 47 and 48, the transport filmis extended by the tractor motor to transport the build material fromthe cartridge to the image plane. Vacuum is applied to secure the filmto the image plane, in a manner described below, and the layer of buildmaterial is imaged onto the build surface. The vacuum is released andthe solenoid poppet pushes the edge of the film upwardly to assist inreleasing the film from the image plane for retraction. The film isretracted into the cartridge, whereupon the cartridge scrapes buildmaterial from the film. The film can then be extended multiple times asneeded between layers or at various stages of the build process and inthe absence of build material for dabbing the build surface to removeexcess uncured build material and return the excess build material tothe cartridge.

Turning now to a discussion of the image plane assembly and theinteraction of the cleaning assembly and transport film with the imageplane, FIGS. 49 through 55D provide isolated views directed to thesefeatures. FIG. 49 provides an overhead perspective view from the upperleft-hand side of an image plane assembly of the invention generally at600 and a cartridge generally at 200. The cartridge assembly 200includes a housing 202 having a lid 204, an upper section 220 and alower section 250. The image plane assembly 600 includes an image plane605 and a frame 610 for containing and supporting the image plane.Radiation-transparent glass typically constitutes the image plane. Theimage plane can be prepared from any material sufficiently strong andtransmissive to the selected solid imaging and curing radiation toenable the apparatus to operate for its intended purpose, includingvarious plastics.

Also illustrated in FIG. 49 is a motorized arm 310 for withdrawing theintra-layer cleaning assembly 300 from the cartridge. It should berecognized that this cleaning assembly is not present in the embodimentof FIG. 3, and that a pull strap would be used to attach to a tractormotor for this purpose, as described in connection with FIGS. 47 and 48above.

Motorized arm 310 has a roller brush or linear brush motor 312 mountedthereto and in contact with the brush (not shown in this view) formingpart of the intra-layer cleaning assembly 300. Motorized arm 310 alsomounts a mechanical lever arm 316 by which the intra-layer cleaningassembly 300 is mounted to the motorized arm.

FIG. 49A is a view similar to that of FIG. 49 and illustrates themotorized arm 310 extending the intra-layer cleaning assembly 300 andattached film 400, coated with build material 410, from the cartridge200 and across the image plane 605. The intra-layer cleaning assembly inthis embodiment included a generally rectangular and open housing 320having three sides, the left-hand side of which is secured by mechanicalarm 316 to motorized arm 310. Housing 320 contains a rotatable rollerbrush 314 in brush-spinning contact with roller-brush spinning motor312. Brush 314 contacts a build after a layer of build material has beencured thereon to remove the excess uncured build material by spinningcontact with the excess, which is uncured material that may remain onthe build surface after illumination and UV curing and potentiallyinterfere with the build's precision.

The roller brush housing 320 mounts opposite the mechanical lever arm316 a transport surface for build material, which is a radiationtransparent flexible film 400. FIG. 49A illustrates film 400 havingbuild material applied thereto on the upwardly facing surface oppositethe image plane 605.

The alternately extendable and retractable transport surface 400 is aflexible film typically composed of one or more fluoropolymer resins,such as poly(propylene), poly(carbonate), fluorinated ethylenepropylene, and mixtures and co-polymers thereof. Polytetrafluoroethylene(PTFE) films including Teflon brand films are useful, in part becausethey release hardened resin well to the build surface. Typically, thefilm is non-elastic. Regardless of the material used, the alternatelyextendable and retractable surface should be at least somewhattransparent such that it transmits sufficient radiation for solidimaging. As used herein, the term “transparent” as used in this contextmeans any suitable material that allows the passage of sufficientradiation (such as UV or visible light) to pass through to effect thephotopolymerization reaction that solidifies the build material. Becausethese transparent materials may be very thin, the term also includestranslucent or partially transparent materials.

The build material 410 can be any of a number of suitable compoundmaterials for solid imaging, commonly referred to as “resins,” with theprimary requirement being that the build material is flowable. The buildmaterial must be capable of being pumped from the lower section 250 ofthe cartridge assembly 200 for application to the film 400 surface in alayer of suitable thickness. The build material must be solidified uponexposure to solid imaging radiation of a preselected wavelength, shouldhave good adherence to the build object and ready release from thetransport film when solidified. The build material contains both UV andvisible light radiation photoinitiators so that it cures upon exposureto both forms of radiation, predominately being cured in its initialliquid state by visible light radiation and in the green statethereafter predominately being cured by UV radiation. Suitable resinsfor use as build materials in the practice of the invention includethose described in U.S. patent application Ser. No. 11/096,739 filedApr. 1, 2005 and entitled “Radiation Curable Compositions Useful InImage Projection Systems,” the contents of which are incorporated hereinby reference in their entirety.

FIG. 49B is a view similar to that of FIG. 49A and illustrates theintra-layer cleaning assembly 300 and attached build material transportfilm, coated with build material, fully extended from the cartridgehousing 202 across the image plane 605 (FIG. 49), which is obscured bythe build material 410 in this view. A two-dimensional image of a layerof a gear wheel 2000 is received from an imager and reflected upwardlythrough the image plane 605, through the transport film 400 (FIG. 49),and to the build material layer 410 on the upper surface of thetransport film. The image cures the build material in the shape 2001 ofthe two dimensional image onto the wetted surface of the build.

FIG. 49C adds the build platform assembly 700 with a build 2002 mountedthereto to the view of FIG. 49B. The build platform assembly 700 lowersthe build in the direction indicated by the arrows into contact with thebuild material layer 410 on the transport surface 400. When the image2001 is irradiated in the fresh build material, the image is cured onthe build surface, thereby adding another layer and building eventuallya three-dimensional object.

FIG. 49D illustrates the build 2002 raised out of contact with thetransport surface 400, the image 2001 having been cured onto the buildsurface from the area of the film 400 containing build material in thatimage, and retraction of the transport surface 400 and excess uncuredbuild material 410 along with the intra-layer cleaning assembly 300. Thecomputer-controlled build platform (FIG. 49C) raises the build to alevel of about one inch for contact of the image surface 2001 with theroller brush 314. Motor 312 spins the brush in contact with the build2002 at the image surface 2001 to remove any uncured build material.

FIGS. 50, 50A, and 50B are sequence views illustrating travel of theintra-layer cleaning assembly 300 and transport film 400 from theirorigin in the cartridge (FIG. 50) over the image plane assembly 600(FIG. 50B) and to the opposite end to suspend the film over the imageplane (FIG. 50C). It should be noted that the opposite ends of the imageplane frame 610 (FIG. 49) are angled to form downwardly sloping surfaces620 and 622 (FIGS. 50, 50A, and 50C).

Intra-layer cleaning assembly 300 has resilient foam blocks 305 placedbetween its lower surface and the film as illustrated so that whenextended to encounter the image plane frame, the foam engages the angledsurface 620 and compresses upwardly to press the film against the imageplane 605. After full extension over the image plane, the foam blocksexpand over the sloped surface 622 to push the film down slightly belowthe surface of the image plane, traveling downwardly on slope 622. Theeffect is analogous to that of tightening a drum head and, along withapplication of vacuum to the film as described below, ensures a securefit of the transport film to the image plane.

The motorized arm 310 (FIG. 49) for the cleaning assembly 300 is drivenby a motor 309 (FIG. 2). Motor 309 is a DC planetary gear motor that canwithstand relatively large torque in drive and reverse without slowingdown. The motor drives a reciprocating carriage for the arm 310 mountedon guides extending across the length of the image plane frame (notshown). At the end of travel, when the film and intra-layer cleaningassembly are situated over the left-most downwardly sloped edge of theimage plane support frame, the motor releases the arm for application ofvacuum and for a tight fit.

The motor 309 does not retract the film and cleaning assembly, which isaccomplished instead by a retracting contact roller 230 in the cartridge(FIG. 23) and a retractor motor 524 on the cartridge frame (FIG. 2).Nevertheless a small electromotive force applied by the motor 309 onretraction assists in overcoming friction forces resisting retraction.

FIGS. 51 and 52 are sequence views similar to FIGS. 50B and 50A,respectively, and illustrate the build platform assembly 700 and build2002 lowered into position on the fully extended and coated transportfilm 400 for irradiation (FIG. 49C) and then raised for intra-layercleaning and retraction and recoating of the transport film (FIG. 49D).The build platform assembly includes a removable and replaceable buildpad 710 with a plurality of discrete discontinuous raised surfaces 715for build supports for securing a build 2002 and a build platformsupporting and securing frame 750 for securing the build platform,discussed in more detail below. Independently operated elevator brackets901, 1001 are attached to elevator assemblies 900, 1000 (FIG. 2),respectively, for raising and lowering the build platform. Again, butfor the absence of the cleaning assembly 300 and features relatedthereto, the features of the embodiment of FIG. 3, including the buildplatform, pad, and elevators can be substantially similar in certainembodiments.

FIGS. 53 and 54 illustrate one embodiment of the attachment of thetransport film 400 to the intra-layer cleaning assembly 300. The film isinserted into a thin sheet-metal clamp fitting 402 by which the film isattached to the intra-layer cleaning assembly. The clamp fitting may bebent downwardly adjacent the film portion extending from the clip topush the film into contact with the image plane, if desired, to reducethe possibility of air entrainment between the film and plane. This bendshould be unnecessary with the embodiment illustrated in FIGS. 50through 50B since the resilient members 305 serve this purpose.

The image plane assembly 600 (FIGS. 2 and 3) is more fully illustratedin FIGS. 55 through 55D for the purpose of showing application of vacuumto the transport film (not shown in these views). FIG. 55 shows theimage plane 605 seated in frame 610 with orifices 630 for mounting theimage plane. Frame 610 provides channels 627 at each interior corner forclearance of the image plane corners. Channels 628 provide forapplication of vacuum to the top surface 625 of the image plane (FIGS.55A, 55B, and 55C) to eliminate air and to retain the transport film inplace during imaging and when lifting the imaged build off the transportsurface. There is a small gap between the upper surface 611 of thevertical wall 629 of the image plane frame and the upper surface 625 ofthe image plane 605 for a vacuum path.

FIGS. 55A through 55C illustrate the vacuum channel in more detail incutaway perspective (FIG. 55A) and in cross section (FIGS. 55B and 55C),showing channels 628 cut into the wall 629 against which the image planeis placed. A horizontally extended edge 629′ supports the image plane sothat the plane does not block the vacuum path between it and wall 629.The edge 629′ supports the image plane to create a small offset gapbetween the top of the image plane 625 and the top of the frame 611 offrom about 0.001 to 0.005 inch so that vacuum drawn through orifice 626(FIG. 55D) runs through the channels 628 and under the transport film todraw the transport film down into the gap between top of the image planeand the top of the frame. Too large a gap and the film will warp at theedges creating a leak path between the film edges and the frame andreducing the vacuum. Too small a gap and the film may not adheresufficiently to the image plane when the build is lifted.

Drawing a vacuum assist on the film removes air that otherwise might betrapped between the transport surface and the planar sheet so that thetransport surface and the build material layer on the transport surfaceare as flat as possible. Drawing a vacuum assist also secures thetransport surface to the planar sheet during imaging and when the buildlifts off the transport film surface. Thereafter, the vacuum can bereleased so that the transfer surface can overcome the shear forces atthe plane for retraction, either by using the solenoid poppet of FIG. 48in the embodiment of FIG. 3 or retraction of the cleaning assembly 300(FIG. 2).

Nipple 626 located on the underside of the image plane support frame(FIG. 55D) provides a point of connection to the vacuum channel 628 fora conduit to a suitable vacuum pump, neither of which conduit and pumpis illustrated. Typically the vacuum pump will be located in anelectrical housing mounted to the modeler, also not shown. The vacuumcan be released simply by providing a vacuum bleed, although it may bedesirable to take additional steps to overcome the shear forces that maydevelop between the film and the rigid planar sheet at the image plane.Positive airflow may be provided by reversing the vacuum pump to assistin overcoming shear forces.

Turning now to the build pad and build pad platform and frame assemblyillustrated at 700 in FIGS. 56 through 58, the build pad 710 is asurface to which a build object or part can be attached. The build padshould have a surface that is adherent to initial build support layers.To facilitate the adhesion of the build material supports to the buildpad, the build pad may include a plurality of structures 715 extendingfrom the planar surface of the build pad, which define a plurality ofdiscontinuous discrete planar surfaces. In the embodiment of the buildpads depicted in FIGS. 56 through 58, these structures extending fromthe build pad take the form of truncated pyramids having a flat surfaceparallel to the surface of the build pad, but the structures may be inthe shape of the tops of cylinders, rectangles, squares, ellipsoids, orany other shape that can extend from the planar surface of the build padto provide support to the build part. In the case that the build pad isconstructed from injection molded plastic, the structures may be shapedsuch that they extend from the surface of the build pad at anon-perpendicular angle sufficient for ready release from the injectionmold. A glass build pad can be constructed with fully cured imagedstructures of any shape providing discontinuous planes for initiatingthe build. Any arrangement, size, and spacing of shapes may be used solong as the structures provide the necessary support base.

In the illustrated embodiments of FIGS. 56 through 58, the truncatedpyramid structures are arranged in a grid pattern, spaced from about0.140 to about 0.562 inches apart. One useful embodiment has thepyramids spaces 0.281 inches apart. The truncated pyramid structures allextend from the surface of the build pad by a single predetermineddistance of about 0.1 inch.

In one embodiment (FIGS. 56, 56A, and 56C), the build pad is illustratedas a transparent pad supported in a frame snap attachment 751 mounted ona ground, flat build platform 750 that is attached to elevator brackets901, 1001, which are attached to a pair of elevator arms 900, 1000,respectively (FIGS. 2 and 3). Cutouts 751′ in the build pad (FIG. 56B)provide a point of attachment for the snap attachment 751. FIG. 56Aprovides a horizontal section through the snap attachments and a portionof the build pad as shown along the arrows in FIG. 56C to illustrateengagement with the cutouts 751′. A vacuum hose 753 (FIGS. 2 and 56) isprovided, connected to a vacuum pump in the electrical housing 128(FIG. 1) for the apparatus, to pull vacuum on the build pad for secureattachment to the build platform.

FIGS. 57 through 57A illustrate an alternative build pad that is nottransparent and, although having a similar pyramid structure 715′ asdescribed above for build supports on the side of the pad facing thebuild (FIG. 57A), the embodiment of these figures includes on theopposite side a plurality of discrete support structures 714 forengaging the ground, flat build platform (FIG. 56), a vacuum orifice711, and a foam seal about the periphery for secure vacuum attachment.The support structures 714 are configured to provide support while atthe same time allowing vacuum to be pulled evenly about the surface ofthe pad. The seal compresses to a point level with the top of thesupport structures on the initial compression stroke of the elevator towhich the build platform is attached, as is described below inconnection with the elevator, thereby setting the seal.

Yet another alternative to the ground, flat build platform of FIG. 56 isillustrated in FIG. 58. An open frame 716 with a hinged portion 718 isprovided for the build pad for removal and replacement of the build pad.A transparent build pad 710 employed in this frame provides forultraviolet (“UV”) cure of the build through the build pad after a layeris imaged. This embodiment is illustrated in FIG. 3 and UV cure isdiscussed below.

FIGS. 59 and 60 illustrate support structures for a build 2002. A seriesof solidified layers of discrete portions of solid imaging buildmaterial 740 (FIG. 59) can be built from these structures 715 (715′ inFIG. 57) extending from the build pad, which form the base of thesupport structure on which the build is produced. From these discreteportions 740 a lattice 748/749 (FIGS. 59 and 60) is constructed byforming a plurality of layers of solidified solid image build materialextending as a plurality of longitudinal members across the discreteportions. The longitudinal members include two series of parallelmembers 748, 749 that intersect to form the lattice separate from andparallel to the build pad. The intersection of the two series oflongitudinal members may be at approximately 90° angles, resulting in asquare grid.

The grid of the lattice may be built so that it diagonally connects thediscrete portions built from the raised structures of the build pad at a45° angle, which is shown in FIG. 60. The lattice may span the extentsof the region to be used for supports for the build part, and may extendseveral pixels beyond such a region to create a buffer, thereby enablingthe supports to firmly adhere to the grid. From the lattice, thesupports are constructed as a plurality of layers of solidified solidimage build material extending as discrete longitudinal spaced-apartmembers that are generally perpendicular to the plane of the lattice. Avariety of solid imaging resins, the same or different, may be used toconstruct the lattice and supports extending from the build pad. Inaddition to separating the build part from the build pad to enable theirradiation of all surfaces of the part, the use of supports furtherprovides structural support during the build for more complexthree-dimensional objects. The use of a raised surface on the build padwith a lattice and supports extending from the raised surface enablesthe secondary or post-cure assemblies to cure all surfaces of the buildpart tack-free, including those surfaces connected to the build pad.

Turning now to a discussion of the elevator assemblies and theiroperation, elevator arms 900, 1000 (FIGS. 2 and 3) move the buildplatform, pad, and thus the build to place the surface of the build intocontact with solid imaging build material, a solidifiable photopolymerbuild material, and after exposure, out of contact with the solidifiablephotopolymer build material as successive layers are formed during thebuilding process. To enable the movement of the build platform towardthe image plane and away from the image plane, a series of independentz-axis elevator assemblies as depicted in FIGS. 2 and 3 are attached tothe build platform by elevator brackets 901, 1001 shown in FIG. 56.

An elevator assembly is illustrated in FIG. 61. Each elevator assemblycomprises an independently-operated stepper motor 1005 or DC servo motorworking in conjunction with a lead screw 1007 to effect the movement ofthe attached build platform along the length of the lead screw. Guideshafts 1009 steer the movement of the attached build platform. The guideshafts secure upper and lower mounting blocks 1111, 1113, respectively,installed within the apparatus. The stepper motor is mounted into astepper motor mounting block 1115 that can travel between the upper andlower mounting blocks along the guide shafts. The lead screw is securedat one end to upper mounting block with the opposite end of the leadscrew having an unconnected floating terminus. The build platform may beconnected to the elevator assemblies by a pair brackets 901, 1001 (FIG.56) extending from the steeper motor mounting blocks and attached to thebuild platform.

Because each elevator assembly moves independently of the other, theposition of the build platform must be initialized prior to any buildprocess to ensure that the build platform is parallel to the imageplane; otherwise, there may not be uniform spacing between the build padand the image plane across the entire build pad, which could causeuneven layer thickness. This initialization is accomplished by means ofa compression stroke of the elevator assembly. During this compressionstroke, the build platform is lowered to the image plane until the buildpad makes contact with the image plane. As the build pad is pressedagainst the image plane, spring-activated plungers 1120 cooperating witha compression switch 1117 secured at the attached end of the lead screwon the upper mounting block of each of the elevator assemblies registerthe forces applied.

In one embodiment, the plunger activates the compression switch 1117 ata force of about 22 pounds or about 97.86 Newtons. A homing switch 1116may also be provided adjacent to the compression switch to indicate thata build platform has reached its uppermost position. The compressionstroke may further serve to set the vacuum seal described above inconnection with FIG. 57 or to detect whether a build pad even ispresent. The performance of the compression stroke may be monitored, andwith at least a close approximation of the relative location of thecomponents, the absence of a build pad could be known if the elevatorassembly is able to move the build platform farther than should bepossible.

After initialization of the platform and pad, the build may progress,starting with the supports. As illustrated in FIG. 62, as the elevatorassemblies cause the build surface to approach the layer of imagingmaterial on the film, it is desirable to tilt the build surface so thatone end engages the image material before the other. The build may thenbe brought to level in the image material layer. A down tilt assists ineliminating bubbles or voids between layers of the build material.Thereafter, the fresh layer of build material is imaged with radiationfrom an imaging light source to solidify the layer onto the buildsurface, as indicated by the arrows in FIG. 62.

It should be recognized that the down tilt action can start with eitherthe left or right elevator moving down first, and the down tilt can bealternated between the left and right elevators during the build to evenout slight differences that may occur between initiating the tilt withone or the other elevator.

Once the layer of resin is cured by the imager, the build object may beseparated from the transport film as illustrated in FIG. 63. Theelevator assemblies move the build platform away from the image plane,allowing the film to return to the cartridge in the direction of thearrow to remove and filter any resin remaining on the coating film. Anun-coating procedure for removal of excess uncured build material may beinitiated, either with the intra-layer coating assembly 300 (FIG. 2) orwith the transport surface extended in the absence of build material(FIG. 3). A post-imaging UV cure, described below, may be performedfurther to harden the resin before re-extending the transport film andrecoating the build with another layer added to the build object.

To avoid undue stress on the build part caused by adhesion of the buildobject to the transport film following the addition of a layer, theelevator assemblies may be used to aid in the separation the buildobject from the coater film by adding a peeling action. This isespecially important for parts with larger cross sections. Just as theelevator assemblies may be operated independently to create a down tiltto eliminate bubbles or voids between layers of the build material, asillustrated in FIG. 62, the elevator assemblies may be operatedindependently to create an up tilt, as shown in FIG. 63 upon completionof the primary cure, FIG. 62. This up tilt serves to break theattractive force created between the transport film and build material,thus reducing the force needed to separate the build part from the shadeand reducing the chance of stressing or breaking features of the build.The up-tilt step may include a horizontal displacement of the buildplatform to avoid distortion, bending, or tearing of build features as aresult of the non-synchronous movement of the independent elevatorassemblies.

The up tilt action can start with either the left or right elevatormoving up first, and the up tilt can be alternated between the left andright elevators during the build to even out slight differences that mayoccur between initiating the tilt with one or the other elevator.

By moving the build platform laterally in a direction corresponding tothe tilt, the entire build object is rotated rather than simply raisingone side, which may cause shearing forces. The horizontal distance theelevator apparatus needs to shift equals the vertical distance one ofthe elevators moves to effect the tilt multiplied by the height of thebuild part all divided by the distance between the elevators. Forexample, if the left elevator is moved up by a distance D to begin therelease process of a part that has a height H, and the two elevators areseparated by a distance W, the build platform should be shifted to theright a distance d=D·H/W. Ideally, the accelerations for the twomovements should be matched. When the part is moved back down to engagethe coated film, the same action of shifting the elevator, and therebythe build part, may be performed in reverse.

Alternatively, the film may be shifted instead of the elevators attachedto the build platform to accomplish the same rotation. Since the filmmay adhere to the image plane, either naturally or due to a vacuum hold,both the coater film and image plane may be moved in the image plane asthe part is pulled away from the coater.

Turning now to the radiation assemblies of the invention, and inparticular that of the imager 1100, FIGS. 64 through 64B illustrate anexploded imager alignment housing. The imager 1100 may be a custom-builtUV projector or laser system or a commercially-available digital lightprocessing (“DLP”) projector with modified optics to display bothunfiltered UV-A and visible light wavelengths, with a desired focallength established based on the arrangement of the flexible transportimaging system, and the light intensity adjusted based on the buildmaterial used. Other useful imagers include liquid crystal display(“LCD”) projectors, liquid crystal on silicon (“LCoS”) projectors, andlight emitting diode (“LED”) projectors, which are similar to LCDprojectors and use bright LED's for the light source instead of an arclamp. DLP projectors made specifically for UV are also contemplated,although the build material may need to be modified to take fulladvantage of the projector. Also contemplated are imager arrays ofUV-only LED's or plasma arrays in projectors with transfer lenses.Traditional CRT projectors can be used with visible and UV or with UVonly.

In one specific embodiment, the imager is a DLP projector having a lampand a nine-element projection lens imaging radiation from the lamp overa spectral range suitable for solid imaging including from 350 to 450 nmin focus at a projection distance of 400 mm over an image area of 9inches by 6.75 inches. The DLP projector may include a UV/IR filter toremove radiation from the lamp outside the desired spectral range. Anillumination lens may be used to uniformly distribute radiation from thelamp across the imaging element. A UV-enhanced light pipeinterconnecting the lamp and the illumination lens and UV-enhancedmirrors in radiation-directing communication with the illumination lensand imaging element may also be provided.

Because an imager has a specific focal length corresponding to the sizeof the build pad, and larger builds therefore require a longer focallength, larger builds would necessitate a correspondingly larger solidimaging apparatus. Alternatively, a series of mirrors 1405, 1407 asillustrated in FIGS. 65 and 66 or a mirror assembly 1399 as illustratedin FIG. 3 are provided to reflect the projected light onto the imageplane within a smaller frame, effectively “bending” the projected lightwithin the apparatus while maintaining a longer focal length.

Image alignment typically will have already been accomplished prior toshipment to the user so that all a user of the apparatus of theinvention has to do is remove and replace a spent imager with a new oneto obtain an aligned image. Imager alignment is accomplished prior topurchase of the imager by the user using an imager alignment fixture andan alignment procedure as described below.

The imager typically has a frame 1109, 1107 into which the imagercomponents are fixed, the frame having alignment members 1106 (FIG. 64A)corresponding to receptacles 1105′ (FIG. 64) in an alignment fixture1105. The receptacles may contain an adhesive to fix the frame securelyin position to the alignment fixture. One embodiment of the alignmentfixture 1105 for three such frame alignment members 1106 and havingalignment fixture receptacles 1105′ is shown in FIGS. 64 through 64B.

The imager alignment fixture may then be precisely aligned andinterlocked to fit within a corresponding alignment fixture 1102 locatedon the solid imaging apparatus (FIGS. 2 and 3). The connection betweenthe corresponding alignment fixtures may be one or more tongues on theimager alignment fixture corresponding to one or more grooves in theapparatus fixture. The housing 1109, 1109′, and 1107 that contains theimager 1100 and the associated alignment fixture 1105 also includesvents for venting heat produced by the imager.

To align and focus the imager prior to shipment to the user, therefore,the imaging alignment fixture should be precisely located, a targetshould be imaged at a fixed distance between the target and the imager,the location of the imager should be adjusted accordingly so that theimage is located precisely on the target, the imager should be focused,and then the alignment fixture should be secured to the adjusted imager.To align the imager in this system, a target fixture may be placed onthe image plane in place of the build pad and the fixture may beadjusted by adjusting the build pad support frame. Thereafter, a buildpad inserted into its corresponding supporting frame by the user will bealigned to the imager.

Once the imager is aligned, and before shipment to the user, the imagermay then be characterized for the gray scale for any pixel in the imageagainst a predetermined threshold of solidification of the borders inthe build. Gray scale adjustment is described in co-pending and commonlyowned U.S. patent application Ser. No. 11/468,090 filed Aug. 29, 2006for “Improved Wall Smoothness,” the contents of which are incorporatedherein by reference in their entirety.

An alternative, although less efficient method of improving the bordersof the build, not necessarily with equivalent results, is to image alayer of build material more than one time, shifting the image in thesubpixel range to achieve better resolution at the boundaries of thebuild, as is described in co-pending and commonly owned U.S. patentapplication Ser. No. 11/096,748 filed Apr. 1, 2005 for Edge Smoothnesswith Low Resolution Projected Images for Use in Solid Imaging,” thecontents of which are incorporated herein by reference in theirentirety.

Turning now to a discussion of the additional radiation assemblies ofthe invention, which are used for a secondary cure to further react anddry the build layers, FIGS. 65 and 66 illustrate schematically ahigh-intensity UV lamp assembly 1500 and an imager 1100. A pair ofmirrors 1405 and 1407 form a mirror assembly located within the desk topmodeler behind a UV shield 1400 (FIG. 2) so as to convey the image tothe image plane in a compact format. Mirror 1405 is fixedly securedwithin the desk top modeler while mirror 1407 is reciprocatingly securedfor moving back and forth by a track wheel 1409.

Mirror 1405 is generally located at an angle from the vertical of about30 degrees and the mirror 1407 is generally located at an angle of about60 degrees from the vertical. Mirror 1407 is reciprocatingly secured foruse in illuminating the image plane assembly 600 when extended (FIG. 65)and illumination of the image plane assembly by the high intensity UVassembly 1500 when retracted (FIG. 66). Reference photo diodes 1401 formonitoring intensity (FIG. 2) are useful for making process adjustmentsdepending on the age of the imager and for monitoring performance of thehigh intensity UV source, both of which usefully may be located in UVshield 1400.

UV sensor/bulb degradation indicators, such as the photo diodesmentioned above, are used primarily to adjust the exposure time toachieve constant exposures. Because the light intensity of an imager anda high intensity UV bulb may fade as the imager ages, the UV sensor/bulbdegradation indicator also can signal when the intensity of the imagerneeds to be increased to counteract any degradation or ultimately whenthe imager or high intensity bulb needs to be replaced.

The intensity of the projected image may be measured and characterizedagainst a gray scale of from black to white of from 0 to 255. The grayscale is measured at one location and the intensity measurement may betaken at 16 different locations selected diagonally across the imageplane from corner-to-corner and horizontally and vertically across theimage plane.

The high intensity UV lamp assembly 1500 comprises a pull out housingframe 1501 (FIG. 2) that can be easily inserted into and removed fromthe desk top modeler for replacement as needed. Within the frame arelocated a high intensity UV bulb 1502 and a parabolic reflector 1503,the bulb being of an intensity capable of curing the build through eachindividual layer to the previously built layer, typically about 600Watts in the embodiment illustrated. A transparent build pad normally isnot needed with a high intensity UV source to achieve athrough-the-build cure. High intensity UV is applied after each layer isinitially cured by the imager 1100 and cleaned by the intra-layercleaning assembly 300 (FIG. 2). The high intensity UV source provides afinal cure that produces a tack-free and fully reacted build.

Through-the-build cure is a function of the available UV energy and thetime it takes to cure through a layer and to obtain a tack-freecondition on the backside of the build, which is the side attached tothe supports on the build pad. Generally speaking, through-the-buildcure can be obtained with a build material of a relatively high degreeof photosensitivity by applying 80 mW/cm2 of UV-A for about 8 seconds,which is about 0.64 J/cm2. A less sensitive build material may requiremore, and so a useful range of UV-A is from about 0.5 to 3 J/cm2,depending on the demands of the specific build material. Amedium-pressure mercury arc lamp having 600 Watts of input power in thereflector illustrated in FIG. 67A can achieve 80 mW/cm2 over a buildarea of 9×6.75 inches, which is 392 cm2, which is a total utilization ofabout 31 Watts of UV-A.

Individual lamps may be more or less efficient, and the invention couldbe practiced with more or less UV-A depending on whether the operatorwanted to speed up or slow down the rate of cure. For example, mercuryarc lamps are available with less power, down to about 300 Watts, orwith more power, up to several thousand Watts. These sources could beused within practical limits on time and cooling and the context of use.Higher power systems may not be compatible with use in a desk-topmodeler for the office.

It should be recognized that a variety of other sources of UV could beused, including those that also provide visible or other radiation,including those mentioned above as imagers, so long as the imager orother source provides sufficient UV to obtain post-curing of a build, asset forth above.

Turning now to a discussion of the operation of the reciprocating mirror1407 (FIGS. 65 and 66) as illustrated in more detail in FIGS. 67 through68, FIG. 67 illustrates image plane assembly 600 mounted atop a housingbox frame 1400, 1402 for the reciprocating mirror 1407. A right-mosttoothed rubber roller wheel 1410 engages a friction track 1412 toretract and extend the mirror. There are two such rollers and tracks,one on the left and one on the right side of the mirror 1407. In FIG.67, the mirror is fully extended for imaging the image plane assembly.In FIG. 67A, the mirror is retracted, exposing the image plane to the UVbulb 1502 and parabolic reflector 1504 below. The roller wheels aredriven by a motor 1425 (FIGS. 2 and 68), which is a DC planetary gearmotor similar to that used to extend the transport film and intra-layercleaning assembly.

A large amount of heat can be generated by the UV bulb, which typicallyremains on at all times during use of the apparatus because it cannot beinstantly turned off and on. The surface of the bulb may approach 1000degrees Fahrenheit or more and the surface of the bulb enclosure mayreach 200 degrees Fahrenheit or more. The apparatus is provided with amultiplicity of cooling channels and fans (as illustrated in oneembodiment at 1600, FIG. 2) for forced air cooling for removing excessheat, and may also be provided with dust filters for intake air andcharcoal filters for odor control, if desired.

For example, a dust filter may be provided on the vented housing floorof the apparatus as illustrated in floor 134′ of FIG. 3. Suitablylocated intake fans pulling air through a dust filter in the housingfloor can discharge into the mirror box frame 1402 and behind the UV boxframe 1500, 1501 (FIG. 67B). A fan can be located inside the UV box toblow air received from the intake fans around the parabolic reflector1503 (FIG. 65) and into the mirror frame box 1400, 1402 (FIG. 67). Themirror box frame should be open to discharge to the surrounding housingthereby to exit the housing. Exhaust fans useful for this purpose andcharcoal filters for odor control may be located at the rear of thehousing.

FIG. 67B illustrates the retracted mirror 1407 and a more detailed viewof the support 1413 for mirror frame box 1415 and the left-most toothedrubber wheel 1409, corresponding to wheel 1410 (FIG. 67A). The mirrorsits atop a box frame element 1415 reciprocatingly mounted in frame 1411atop mirror frame 1402 in support 1413. A section through the toothedwheel 1409 illustrates electrical connection with a motor M (component1425 in FIG. 2) and the relationship of the friction track 1416, mirror1407, and mirror support frame 1413.

An alternative fixed mirror assembly 1399 comprising a similar pair ofmirrors is shown in FIG. 3. In the alternative arrangement of FIG. 3,the mirrors of mirror assembly 1399 are fixed at a similar angle tothose of FIGS. 2 and 65 and are not retractable for reciprocatingoperation since no separate UV source is located below the mirrors.Instead, UV for post-curing, if any, is provided through the image planeby the imager via the mirrors and additional UV sources, halo assembly1500′ and hood assembly 1500″ as described below and in connection withFIG. 3 above.

FIG. 69 illustrates halo assembly 1500′. The halo assembly travels on astepper motor-and-guide-rod elevator 1501′ to provides UV radiation at asomewhat lower intensity of about 100 Watts to the vertically orientedsurfaces of the build. UV bulbs 1502′ contained in a frame 1503′surround the vertical surfaces of the build with UV radiation.

FIG. 70 illustrates hood assembly 1500″, which includes UV bulbs 1502′of about 100 Watts mounted to a frame 1503″ (shown in exploded view)that has a lever arm and motor assembly 1504″ (also shown in explodedview) for providing UV radiation through a transparent build pad (FIG.58) to the supports and initial build layers.

The invention has been described with specific reference to preferredembodiments. However, variations can be made within the spirit and scopeof the invention as described in the foregoing specification as definedin the appended claims.

What is claimed is:
 1. A method for facilitating release of a buildobject on a build platform in a solid imaging device from an image planein the solid imaging device, said method comprising the steps of: a)solidifying solid image build material on the image plane to the buildobject to define a layer of the build object; b) tilting with respect tothe image plane the build platform to lift one edge of the build objectoff the image plane, wherein tilting of the build platform is performedwhile lifting the build object from the image plane; and c) repeatingsteps (a) and (b) for at least one additional layer of the build object.2. The method of claim 1 wherein the steps (a) through (b) are repeated,alternately lifting a first and a second edge.
 3. The method of claim 1wherein said image plane further comprises a flexible build materialtransport surface on a rigid surface transparent to solid imagingradiation and said method further comprises the steps of adhering thetransport surface to the rigid surface, contacting a layer of buildmaterial on the build material transport surface opposite the rigidsurface with the build, and imaging the layer to solidify the layer, andwherein said step of tilting the build platform lifts one edge of thebuild off the transport surface.
 4. The method of claim 3 furthercomprising the steps of lifting the build off the transport surface andthereafter releasing the transport surface from the rigid surface. 5.The method of claim 1 wherein tilting the build platform to lift oneedge of the build object breaks an attractive force between the curedbuild material and the surface to which it is adhered.
 6. The method ofclaim 5 wherein the surface to which the cured build material is adheredis a transport film.
 7. The method of claim 1 further comprisinghorizontally displacing the build platform relative to the image planewhile tilting the build platform.
 8. The method of claim 7 whereinhorizontally displacing the build platform avoids at least one ofdistorting, bending, or tearing features of the build object.